1. Field of the Invention
The present invention relates to a surface fastener formed of fibers wherein necessary engaging strength is ensured, the surface fastener is flexible and is excellent in touch, and peeling of the surface fastener can be carried out smoothly.
2. Description of the Related Art
A conventionally and widely known typical surface fastener formed of fibers has female or male engaging elements obtained by weaving/knitting at the time of weaving/knitting of a foundation cloth. The female engaging elements are normally in a shape of loops formed of multifilament and the male engaging elements are in a hook shape or a mushroom shape.
Normally, the male engaging elements of the surface fastener are formed of a monofilament having a large diameter, and the hook-shaped or mushroom-shaped male engaging elements of the male surface fastener are engaged with and disengaged from the loops as a large number of female engaging elements of the female surface fastener. Therefore, in order to ensure necessary engaging strength with which the male engaging elements are engaged with the mating loops by using a single monofilament for the male engaging element, the monofilament is required to be rigid to some degree and to have a large diameter. As a result, the male surface fastener is rough and hard to the touch, and in addition, a noise is liable to be generated when the male engaging elements are disengaged from the female engaging elements.
It is known that the mushroom-shaped engaging element is superior in engaging strength to the hook-shaped engaging element and that the mushroom-shaped engaging element can be engaged with the opposite loop in every direction because an engaging head of the mushroom-shaped engaging element bulges in every direction when comparisons are made between the hook-shaped engaging element and the mushroom-shaped engaging element of the same material and with the same diameter. As a result, because the same engaging strength can be obtained even when the diameter of the mushroom-shaped engaging element is smaller than that of the hook-shaped engaging element, the mushroom-shaped engaging element is superior in flexibility to the hook-shaped engaging element when the mushroom-shaped engaging element has the same engaging strength as the hook-shaped engaging element.
However, because the engaging head itself of the mushroom-shaped engaging element is not elastically deformed, a surface of the surface fastener is prickly to the touch. Furthermore, because the mushroom-shaped engaging element is engaged with the mating loop in such a manner that the loop is wound around a neck portion of the engaging head of the mushroom-shaped engaging element, i.e., the mushroom-shaped engaging element is hung by its neck portion, the neck portion is liable to be cut in engagement and disengagement of the surface fastener or the mating loop is cut, and thus, the surface fastener with the mushroom-shaped engaging elements lacks durability.
In such present circumstances, because the surface fastener is frequently applied to a portion of a diaper, sportswear, underwear, or the like, the portion being in direct contact with skin, a surface fastener formed of fibers which is flexible, excellent in the touch, and has necessary engaging strength, and wherein little noise is generated in peeling is demanded. In order to satisfy such a demand, a male surface fastener which is flexible and excellent in the touch and has necessary engaging strength is disclosed in Japanese Patent Publication No. 47-9390, for example.
According to the Japanese Patent Publication No. 47-9390, twisting of 200 T/m or more is applied to three to ten filaments having diameters of 50 to 200 D so as to form a pile yarn. The pile yarns are planted into a substrate to form a substrate sheet having on a surface thereof a large number of loops. After heating the substrate sheet to fix forms of the loops and the twist thereof, a top portion or a leg portion of each the loop is cut. The cut loops are opened to produce a surface fastener having a plurality of hooks with a small diameter which stand from a position of the substrate. With the surface fastener having the above structure, engaging strength of each the hook can be decreased to facilitate peeling, generation of a strange peeling noise can be diminished, and an engaging rate of the hooks with the loops can be increased to increase the total engaging strength.
In the surface fastener disclosed in the above Japanese Patent Publication No. 47-9390, however, because a twisted form remains certainly in each the fiber constituting the hook as shown in the drawings, a form of the engaging head of the hook is not stable, and in addition, uniform engaging strength of the hooks can not be expected because of an intricate shape of the hooks. Although coming off of the hooks is prevented by applying resin finish to the substrate in case that the substrate is a cloth formed by weaving/knitting, a base end portions of the plurality of hooks standing up from one and the same position of the substrate are merely fixed in a twisted state. Therefore, although rigidity can be expected in the base end portion to some extent in the beginning of use of the surface fastener, the twist is liable to be removed as a result of repeated use. Once the twist is removed, the base end portion is separated into individual fibers. Because each the individual hook can not have necessary rigidity, the hook is easily bent when the hooks are pushed against the mating surface fastener to engage the hooks with the loops, and thus, the hook can not be engaged with the loop. As a result, a total engaging rate is reduced and the engaging strength which is required of the surface fastener is also reduced suddenly.
The present invention has been developed to solve the above problems, and specifically, it is an object of the invention to provide a surface fastener, wherein necessary engaging strength can be maintained for a long term, the surface fastener has sufficient flexibility even though male engaging elements are formed of fibers and is comfortable to the touch without a prickly feeling, and a strange peeling noise is not generated in addition.
According to a first aspect of the invention, there is provided a surface fastener formed of fibers including at least a large number of male engaging elements planted on a foundation cloth which is a woven or knitted fabric or a non-woven fabric and is formed of fibers, the surface fastener being engaged with and disengaged from a mating surface fastener, wherein the surface fastener has groups each consisted of a plurality of male engaging elements having a small diameter of wire and standing up from a common position of a face of the foundation cloth with respective base end portions of the male engaging elements being in adjacent to each other, and the base end portions of the adjacent male engaging elements are joined by a part of a backing agent which penetrates the woven or knitted foundation cloth.
In this invention, because the groups each consisted of the plurality of male engaging elements stand up from the same position of the foundation cloth formed of fibers, the plurality of male engaging elements standing up from the same position are engaged with the large number of loops on the mating female surface fastener even when the diameter of the male engaging elements is an integral submultiple of the conventional diameter. As a result, the engaging rate is improved and a desired total necessary engaging strength can be applied to the male surface fastener. Because the male engaging elements are secured and integrated by bonding by a part of the backing agent at the base end portion of the group, rigidity of the base end portion of the entire group is increased. As a result, the male engaging elements do not fall down easily in engaging the surface fasteners by pushing the male surface fastener and the mating female surface fastener against each other, thereby improving the engaging rate of the male engaging elements with the mating loops and ensuring the total engaging strength.
Preferably, each of the male engaging elements constituting the group are in a hook shape. As this type of male engaging element formed of fiber, there is a mushroom-shaped engaging element in addition to the hook-shaped engaging element. However, because a cap-shaped or a spherical engaging head which is hung by its neck portion at the time of disengagement from the mating loop is liable to be cut in case of the mushroom-shaped male engaging element, while the hook-shaped male engaging elements are less prickly to the touch and the loops can be easily disengaged from the hook-shaped male engaging elements due to elastic deformation of the hook-shaped male engaging elements as compared with the mushroom-shaped male engaging elements, the male engaging elements are preferably in the hook shape. Needless to say, the mushroom-shaped male engaging elements are not eliminated from the invention.
Further preferably, engaging heads of the plurality of hook-shaped engaging elements constituting each of the groups are orientated in different directions at an angle in a range of 0xc2x0 to 90xc2x0 from each other about a base end portion of the group as a center. As the engaging heads of the plurality of hook-shaped engaging elements constituting each of the groups are in many orientations, engaging rate with the mating loops in random orientations is increased and peeling force acts uniformly in many directions.
Also preferably, at least one of the respective male engaging elements constituting the group has a larger diameter than the rest of the engaging elements. With the male engaging elements constituting the group having different diameters, the engaging strength is ensured and the entire engaging face is flexible to the touch.
Still preferalby, at least one of the male engaging elements constituting the group is higher than the rest of the engaging elements. As the plurality of male engaging elements constituting the group have different heights, the male engaging elements are engaged with the loops with different heights at the same position of the mating female surface fastener, thereby increasing the total engaging strength.
Preferably, loop-shaped female engaging elements are mixed on the face of the foundation cloth. With the male and female engaging elements being mixed on the surface of the same foundation cloth, it is unnecessary to control the male and female engaging elements separately from each other and it is unnecessary to distinguish the male and female surface fasteners from each other when it is attached to a product.